1. Field of the Invention
This invention relates to a structure of base of column and a construction method for base of column, in which a lower end of column steel frame is installed on a foundation of building.
2. Description of Prior Art
FIG. 3 is a general schematic view of a foundation constructed in the ground, in which a large number of foundations 1 are constructed along an external shape of building with intervals put between them and underground beams 2 connecting these foundations 1 are constructed.
Each foundation 1 is formed into a convex shape by a lower base concrete 4 and a column-shaped foundation concrete 5 placed on it. A column steel frame for each column is placed on top of the foundation concrete 5 to compose the base of column. As the structure of base of column and construction method for base of column, there are a fixed-type base of column system in which the column steel frame is fixed rigidly on the foundation 1 and a pin-type base of column system in which the column steel frame is connected through the pin rotatably to some extent.
In the later pin-type system, the foundation can be made small in its size because a load of building is carried mainly by beams between columns, however, the beams themselves become large so that weights of beam steel frame etc. on the ground increase and the ground work becomes troublesome.
In the former system, the beam between columns can be made small in its weight and size because the load of building is carried mainly by the columns. FIG. 10 shows a conventional example of the fixed beam of column.
Plural anchor bolts 8 together with plural column main reinforcing-bars 6 are incorporated in the concrete 5 of the foundation 1. The column main reinforcing-bars 6 have lower-end bent portions 6a, are arranged into a rectangular shape viewing from above and bound by hoop reinforcing-bars 7, and the entire column main reinforcing-bars 6 are buried in the foundation concrete 5 up to their upper edges. The anchor bolts 8 are disposed at eight places, for example, and supported by a support frame 9. Their upper ends protrude upward from a top face 11 of the foundation concrete 5 so as to be combined with a base plate 14 of the column steel frame 12 by nuts 13. The frame 9 holds the anchor bolts 8 with specified spaces put between them and functions effectively against an upward tension.